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<jats:title>Abstract</jats:title> <jats:p>The Atacama Large Millimeter/submillimeter Array can achieve unprecedented spatial resolutions of 15 to 5 mas with the longest baselines of 16 km and observing at the highest frequencies of 275–950 GHz (1.09–0.30 mm). Two conditions are paramount for successful observations at these frequencies: a phase calibrator in close proximity to the science target and a stable-enough atmosphere to provide a low residual phase rms post-phase-referencing. We investigate the effect of phase-referencing cycle times, for in-band and band-to-band (B2B) observing techniques, using close and distant phase calibrators, at bands 7, 8, and 9 for baselines &gt;2000 m. We find that (1) the phase rms estimated from baselines longer than the effective baseline increases as a function of <jats:inline-formula> <jats:tex-math> <?CDATA $\sqrt{{\rm{time}}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msqrt> <mml:mi mathvariant="normal">time</mml:mi> </mml:msqrt> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsac3b57ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. (2) The expected coherence estimated using the expected phase rms corresponds well to the achieved image coherence. (3) Faster phase-referencing cycle times (&lt;1 minute) improve phase calibration accuracy and image coherence when close phase calibrators (&lt;2°) are used. (4) For cycle times &lt;2 minutes the negative impact of distant phase calibrators dominates the phase error budget. We also explore whether a theoretical parameterization of the effective baseline used to estimate the phase rms and a phase stability measurement, combined with an empirical parameterization of coherence degradation as a function of calibrator separation, is suitable in estimating the expected coherence of target images. The latter proves to be more accurate. Finally, we illustrate a pragmatic approach in establishing an optimal observing strategy via dynamic cycle times and on-calibrator scan lengths.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The identification and analysis of different variable sources is a hot topic in astrophysical research. The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) spectroscopic survey has accumulated a mass of spectral data but contains no information about variable sources. Although a few related studies present variable source catalogs for the LAMOST, the studies still have a few deficiencies regarding the type and number of variable sources identified. In this study, we present a statistical modeling approach to identify variable source candidates. We first cross-match the Kepler, Sloan Digital Sky Survey, and Zwicky Transient Facility catalogs to obtain light-curve data of variable and nonvariable sources. The data are then modeled statistically using commonly used variability parameters. Then, an optimal variable source identification model is determined using the Receiver Operating Characteristic curve and four credible evaluation indices such as precision, accuracy, recall, and F1-score. Based on this identification model, a catalog of LAMOST variable sources (including 631,769 variable source candidates with a probability greater than 95%, and so on) is obtained. To validate the correctness of the catalog, we perform a two-by-two cross-comparison with the Gaia catalog and other published variable source catalogs. We achieve the correct rate ranging from 50% to 100%. Among the 123,756 sources cross-matched, our variable source catalog identifies 85,669 with a correct rate of 69%, which indicates that the variable source catalog presented in this study is credible.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The dust extinction laws and dust properties in M31 are explored with a sample of reddened O-type and B-type supergiants obtained from the Local Group Galaxies Survey (LGGS). The observed spectral energy distributions (SEDs) for each tracer are constructed with multiband photometry from the LGGS, PS1 Survey, UKIRT, PHAT Survey, Swift/UVOT, and XMM-SUSS. We model the SED for each tracer in combination with the intrinsic spectrum obtained from the stellar model atmosphere extinguished by the model extinction curves. Instead of mathematically parameterizing the extinction functions, the model extinction curves in this work are directly derived from the silicate–graphite dust model with a dust size distribution of <jats:inline-formula> <jats:tex-math> <?CDATA ${dn}/{da}\sim {a}^{-\alpha }\exp (-a/0.25),\,0.005\lt a\lt 5\,\mu {\rm{m}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="italic">dn</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi mathvariant="italic">da</mml:mi> <mml:mo>∼</mml:mo> <mml:msup> <mml:mrow> <mml:mi>a</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mi>α</mml:mi> </mml:mrow> </mml:msup> <mml:mi>exp</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mo>−</mml:mo> <mml:mi>a</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mn>0.25</mml:mn> <mml:mo stretchy="false">)</mml:mo> <mml:mo>,</mml:mo> <mml:mspace width="0.50em" /> <mml:mn>0.005</mml:mn> <mml:mo>&lt;</mml:mo> <mml:mi>a</mml:mi> <mml:mo>&lt;</mml:mo> <mml:mn>5</mml:mn> <mml:mspace width="0.50em" /> <mml:mi>μ</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsac3bc6ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. The extinction tracers are distributed along the arms in M31, with the derived Milky Way (MW)–type extinction curves covering a wide range of <jats:italic>R</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub> (≈ 2–6), indicating the complexity of the interstellar environment and the inhomogeneous distribution of interstellar dust in M31. The average extinction curve with <jats:italic>R</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub> ≈ 3.51 and dust size distribution <jats:inline-formula> <jats:tex-math> <?CDATA ${dn}/{da}\sim {a}^{-3.35}\exp (-a/0.25)$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="italic">dn</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi mathvariant="italic">da</mml:mi> <mml:mo>∼</mml:mo> <mml:msup> <mml:mrow> <mml:mi>a</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>3.35</mml:mn> </mml:mrow> </mml:msup> <mml:mi>exp</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mo>−</mml:mo> <mml:mi>a</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mn>0.25</mml:mn> <mml:mo stretchy="false">)</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsac3bc6ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> is similar to that of the MW but rises slightly less steeply in the far-UV bands, implying that the overall interstellar environment in M31 resembles the diffuse region in the MW. The extinction in the <jats:italic>V</jats:italic> band of M31 is up to 3 mag, with a median value of <jats:italic>A</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub> ≈ 1 mag. The multiband extinction values from the UV to IR bands are also predicted for M31, which will provide a general extinction correction for future works.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Understanding the preferences of transient types for host galaxies with certain characteristics is key to studies of transient physics and galaxy evolution, as well as to transient identification and classification in the LSST era. Here we describe a value-added database of extragalactic transients—supernovae, tidal disruption events, gamma-ray bursts, and other rare events—and their host galaxy properties. Based on reported coordinates, redshifts, and host galaxies (if known) of events, we cross-identify their host galaxies or most likely host candidates in various value-added or survey catalogs, and compile the existing photometric, spectroscopic, and derived physical properties of the host galaxies in these catalogs. This new database covers photometric measurements from the far-ultraviolet to mid-infrared. Spectroscopic measurements and derived physical properties are also available for a smaller subset of hosts. For our 36,333 unique events, we have cross-identified 13,753 host galaxies using host names, plus 4480 using host coordinates. Besides those with known hosts, there are 18,100 transients with newly identified host candidates. This large database will allow explorations of the connections of transients to their hosts, including a path toward transient alert filtering and probabilistic classification based on host properties.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We describe the timing system and the timing calibration results of the three payloads on board the Insight-Hard X-ray Modulation Telescope (Insight-HXMT). These three payloads are the High Energy X-ray telescope (HE; 20–250 keV), the Medium Energy X-ray telescope (ME; 5–30 keV), and the Low Energy X-ray telescope (LE; 1–10 keV). We present a method to correct the temperature-dependent period response and the long-term variation of the onboard crystal oscillator, especially for ME, which does not carry a temperature-compensated crystal oscillator. The times of arrival (ToAs) of the Crab pulsar are measured to evaluate the accuracy of the timing system. As the ephemeris of the Crab pulsar given by the Jodrell Bank Observatory has systematic errors around (Rots et al. 2004) 40 <jats:italic>μ</jats:italic>s, we use the quasi-simultaneous observations of the X-ray Timing Instrument (XTI) on board the Neutron star Interior Composition Explorer (NICER) to produce the Crab ephemerides and to verify the timing system of Insight-HXMT. The energy-dependent ToAs’ offsets relative to the NICER measurements including the physical and instrumental origins are about 24.7 <jats:italic>μ</jats:italic>s, 10.1 <jats:italic>μ</jats:italic>s, and 864.7 <jats:italic>μ</jats:italic>s, and the systematic errors of the timing system are determined to be 12.1 <jats:italic>μ</jats:italic>s, 8.6 <jats:italic>μ</jats:italic>s, and 15.8 <jats:italic>μ</jats:italic>s, for HE, ME, and LE, respectively.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this paper we introduce the Farpoint simulation, the latest member of the Hardware/Hybrid Accelerated Cosmology Code (HACC) gravity-only simulation family. The domain covers a volume of (1000<jats:italic>h</jats:italic> <jats:sup>−1</jats:sup> Mpc)<jats:sup>3</jats:sup> and evolves close to two trillion particles, corresponding to a mass resolution of <jats:italic>m</jats:italic> <jats:sub> <jats:italic>p</jats:italic> </jats:sub> ∼ 4.6 × 10<jats:sup>7</jats:sup> <jats:italic>h</jats:italic> <jats:sup>−1</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. These specifications enable comprehensive investigations of the galaxy–halo connection, capturing halos down to small masses. Further, the large volume resolves scales typical of modern surveys with good statistical coverage of high-mass halos. The simulation was carried out on the GPU-accelerated system Summit, one of the fastest supercomputers currently available. We provide specifics about the Farpoint run and present an initial set of results. The high mass resolution facilitates precise measurements of important global statistics, such as the halo concentration–mass relation and the correlation function down to small scales. Selected subsets of the simulation data products are publicly available via the HACC Simulation Data Portal.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a collection of 991 heartbeat star (HBS) candidates found in the Optical Gravitational Lensing Experiment (OGLE) project data archive. We discuss the selection process of the HBS candidates and the structure of the catalog itself. It consists of 512 stars located toward the Galactic bulge, 439 stars located in the Large Magellanic Cloud, and 40 in the Small Magellanic Cloud. The collection contains two large groups of HBSs with different physical properties. The main distinction between the two groups is the evolutionary status of the primary star. The first group of about 100 systems contains a hot main-sequence or a Hertzsprung-gap primary star, while the second group of about 900 systems includes a red giant. For each star, we provide two-decade-long time-series photometry, in the Cousins <jats:italic>I</jats:italic>- and Johnson <jats:italic>V</jats:italic>-band filters, obtained by the OGLE project. We also present basic observational information as well as orbital parameters derived from the light-curve modeling.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report new experimental hyperfine structure (HFS) constants of neutral and singly ionized scandium (Sc <jats:sc>i</jats:sc> and Sc <jats:sc>ii</jats:sc>). We observed spectra of Sc–Ar and Sc–Ne hollow cathode discharges in the region 200–2500 nm (50,000–4000 cm<jats:sup>−1</jats:sup>) using Fourier transform spectrometers. The measurements show significant HFS patterns in 1431 spectral lines fitted in our 12 spectra given in Table 1. These were fitted using the computer package Xgremlin to determine the magnetic dipole hyperfine interaction constant (A) for 185 levels in Sc <jats:sc>i</jats:sc> and 6 levels in Sc <jats:sc>ii</jats:sc>, of which 80 Sc <jats:sc>i</jats:sc> levels had no previous measurements. The uncertainty in the HFS A constant is between 1 × 10<jats:sup>−4</jats:sup> and 5 × 10<jats:sup>−4</jats:sup> cm<jats:sup>−1</jats:sup>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the spectroscopic discovery of 69 quasars at 5.8 &lt; <jats:italic>z</jats:italic> &lt; 7.0, drawn from the Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP) imaging survey data. This is the 16th publication from the Subaru High-<jats:italic>z</jats:italic> Exploration of Low-Luminosity Quasars (SHELLQs) project, and it completes identification of all but the faintest candidates (i.e., <jats:italic>i</jats:italic>-band dropouts with <jats:italic>z</jats:italic> <jats:sub>AB</jats:sub> &lt; 24 and <jats:italic>y</jats:italic>-band detections, and <jats:italic>z</jats:italic>-band dropouts with <jats:italic>y</jats:italic> <jats:sub>AB</jats:sub> &lt; 24) with Bayesian quasar probability <jats:inline-formula> <jats:tex-math> <?CDATA ${P}_{Q}^{B}\gt 0.1$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>P</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>Q</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>B</mml:mi> </mml:mrow> </mml:msubsup> <mml:mo>&gt;</mml:mo> <mml:mn>0.1</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsac3d31ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> in the HSC-SSP third public data release (PDR3). The sample reported here also includes three quasars with <jats:inline-formula> <jats:tex-math> <?CDATA ${P}_{Q}^{B}\lt 0.1$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>P</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>Q</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>B</mml:mi> </mml:mrow> </mml:msubsup> <mml:mo>&lt;</mml:mo> <mml:mn>0.1</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsac3d31ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> at <jats:italic>z</jats:italic> ∼ 6.6, which we selected in an effort to completely cover the reddest point sources with simple color cuts. The number of high-<jats:italic>z</jats:italic> quasars discovered in SHELLQs has now grown to 162, including 23 type II quasar candidates. This paper also presents identification of seven galaxies at 5.6 &lt; <jats:italic>z</jats:italic> &lt; 6.7, an [O <jats:sc>iii</jats:sc>] emitter at <jats:italic>z</jats:italic> = 0.954, and 31 Galactic cool stars and brown dwarfs. High-<jats:italic>z</jats:italic> quasars and galaxies compose 75% and 16%, respectively, of all the spectroscopic SHELLQs objects that pass our latest selection algorithm with the PDR3 photometry. That is, a total of 91% of the objects lie at <jats:italic>z</jats:italic> &gt; 5.6. This demonstrates that the algorithm has very high efficiency, even though we are probing an unprecedentedly low luminosity population down to <jats:italic>M</jats:italic> <jats:sub>1450</jats:sub> ∼ −21 mag.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This work searches for the candidates of Galactic disk star clusters in Gaia Early Data Release 3 (Gaia EDR3) and determines their basic parameters from color–magnitude diagrams (CMDs). A friends-of-friends method for membership determination and stellar population models including binary stars (ASPS) and rotating stars are adopted. As a result, 868 new star cluster candidates are found, besides 2729 known ones. When checking the CMD of each candidate, 61 new candidates show main sequences including a turnoff, which suggests that they are real star clusters. The basic parameters, including distance modulus, color excess, metallicity, age (or age range), primordial binary fraction, and rotating star fraction, are determined carefully by fitting the morphologies of CMDs of 61 newly identified star clusters and 594 known star clusters, which have relatively clear main sequences. The CMDs are fitted in considerable detail to ensure the reliability of property parameters of clusters. All final results are included in a new star cluster catalog, which is named LI team’s Star Cluster (LISC), and the catalog is available in the Zenodo repository.</jats:p>